The present invention relates to means for interconnecting high lead count very large scale integrated circuit packages to the conductors of a printed circuit test board. More specifically, the present invention relates to techniques for demountably connecting the integrated circuit packages to the conductors of the circuit board without the use of soldering or of lead forming operations or other such conventional interconnection techniques.
Incorporation of very high speed integrated circuit (VHSIC) chips into modern military electronic systems presents several major printed circuit board level packaging problems. Each printed circuit board will have mounted thereon a large number of VHSIC packages, each of which has a very high lead count, with by way of example as many as 140 packages mounted on a single circuit board with each package having a lead count ranging from 42 to 224. Such high density packaging and associated lead counts generally utilize a multi-layer board to minimize the total area of the board. The packages themselves have closely spaced leads typically about 0.020 inch center to center, which makes the leads difficult to solder onto the board and very difficult to remove for rework or repair. A second problem that such high lead count packages present is in routing the conductors for such a multi-layer board. At least in the initial system development stages, there are invariably changes in the routing, and circuit design changes made after the printed circuit board has been completed. A large board with many such packaged components becomes a very valuable piece of work in progress and only a limited number of board repairs are possible because of the package density with a limited number of circuit track cuts and jumpers utilized to effect circuit changes. It is not uncommon for a partially tested large board with many such circuit packages and changed circuit patterns with many cuts and jumpers affecting the circuit changes to be shifted to a new board which must be routed incorporating all of the changes in all of the components which must be unsoldered from the initial test board and put onto the new board.
U.S. Pat. No. 4,164,033 teaches an integrated circuit package and connector for demountably attaching that package to a printed circuit board panel. The connector includes a base receptacle mounted on the printed circuit board panel for receiving the integrated circuit package, so that microstrip leads on the package are registered with the terminal pads provided on the PC board. The circuit package is also provided with a flexible microstrip terminal which serves to electrically interconnect the leads to the internal circuitry of the chip mounted within the package.
An improved package is desired for large scale integrated circuit chip mounting which permits readily demountable connection of the package to the printed circuit board for test of either the packaged chip individually or of the multi-package system within which the package is one component.